The largest lithium users at present are glass and ceramic industry as well as battery industry, the share of which is constantly growing, because lithium batteries have a significant role in the development of electric automobiles, for example. Part of the lithium is used as lithium carbonate, or it is at least a commercial intermediate product. Lithium is typically used for instance in the batteries of videos, cameras and mobile phones. Natural lithium-containing minerals are mainly spodumene, petalite and lepidolite. In salt lakes, the hypolimnion may also contain lithium, but there the decisive factor with respect to industrial production is the lithium-magnesium ratio. Likewise, also sea water contains lithium. Lithium is produced by heating and further leaching for example ores or concentrates, such as spodumene, i.e. lithium aluminum silicate (LiAlSi2O6) or petalite (LiAlSi4O10). In the first recovery step of lithium, the α structure of spodumene is transformed into a soluble β structure. This can be carried out by thermal heating. It has been found out that the alpha structure is converted into a beta structure when the temperature is 850-1000° C. To summarize: in lithium recovery, lithium mineral is concentrated, whereafter the treatment of the concentrate generally includes transformation of the crystal structure at a high temperature, pressure leaching, carbon dioxide treatment, as well as filtering and cleaning of the created lithium bicarbonate LiHCO3.
From the Canadian publication CA 1297265, there is known a process for producing lithium carbonate. According to said publication, the material is thermally treated in a circulating fluidized bed reactor, which requires a high free-space velocity for the gas in the reactor. The concentrate or ore is fed into the process as coarse material, with a grain size of 1-10 millimeters approximately. In order to make said material circulate in a way characteristic for a circulating fluidized bed, a large gas flow is required. The heating of a large gas flow in turn demands a large quantity of energy. In order to maintain the temperature on the level required by the conversion throughout the whole process, oxygenous gas must be added on different levels. For keeping the gas temperature on a sufficiently high level, a large number of lances is needed for fuel supply. In addition, the high energy demand and large quantity of fuel increase CO2 emissions.